The determination of the increase or decrease of an indigenous cell population in media, such as fluids or air, present in the ambient environment entails great difficulties for a variety of reasons. Amongst them that it is difficult, and sometimes impossible, to distinguish between the numerous species present in the ambient environment. This makes the design of a specifically tailored method for testing the presence of the cells extremely difficult.
Furthermore, many of the systems of interest such as water and oil reservoirs and gaseous environments are continuous flow systems In such systems it is extremely difficult to account for increases and decreases in cell numbers due to the inherent characteristics of the medium.
Moreover, in other instances the organisms grow in the medium in an anchored state, e.g., in the form of a biofilm. Repeated attachment and detachment of the organisms or cells in fact confounds the determination of cell counts or other properties in the biofilm.
In copending U.S. application Ser. No. 201,994 filed June 3, 1988 now U.S. Pat. No. 4,912,332 by Characklis et al, entitled "NON-DESTRUCTIVE METHODS FOR DETECTING ORGANIC DEPOSITS AND REMOVING THEM", a non-destructive method for the in situ detection of organic materials, including cells, which deposit on the internal surface of a conduit through which a fluid flows was described. The detection is undertaken by means of light absorption spectrometry such as infrared (IR) spectroscopy or ultraviolet (UV) spectroscopy.
Therefore, a need still exists for a method of determining the quality of a liquid capable of supporting cellular growth by means of an exogenous cell population which can be placed in contact with the medium in situ for a desired period of time whereas the measurements of the variables are conducted away from the site.